Curable resin composition comprising N-(alkenylphenyl)maleimide, epoxy composition and polyamine

ABSTRACT

Disclosed is a curable resin composition comprising (a) at least one maleimide compound selected from the group consisting of N-(alkenylphenyl)maleimide derivatives, and dimers and polymers thereof and (b) one or more kinds of epoxy resins, each having at least one epoxy group in the unit molecule thereof. The resin composition may contain, besides the above two components, an amino compound as a further component (c). The resin composition may comprise a prepolymer of any two components among the three components (a), (b) and (c) and the remaining component. The resin compositions are useful as molding materials, for the fabrication of laminates, and as varnishes, including insulation varnishes and impregnating varnishes.

This is a division of application Ser. No. 312,959, filed Oct. 20, 1981now U.S. Pat. No. 4,401,777.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

This invention relates to a resin composition capable of yielding acured material excellent in heat resistance, and more particularly, itrelates to a curable resin composition capable of providing varnish ofimproved workability and stability as well as formed products ofexcellent curability and physical and chemical properties.

(2) Description of the Prior Art

Maleimide-type resins are known as resins having excellent resistance toheat and are used, for example, in the form of polymaleimide resin whichis a homopolymer of a maleimide compound or polymaleimide-polyamine typeresin which is a copolymer with an amine. These maleimide-type resinscan generally provide satisfactory properties with respect to resistanceto heat. However, prior to polymerization, such maleimide compounds havea high melting point and, moreover, can be hardly dissolved in anorganic solvent commonly used for the production of varnish andlaminates. Due to the above-described nature of maleimide compounds,they are accompanied by a drawback that they must be dissolved in apolar solvent having a high boiling point and high hygroscopicity priorto their application. Thus, an impregnating varnish may be prepared fromsuch a maleimide compound by using a polar solvent represented byN-methyl-2-pyrrolidone, N,N-dimethylacetamide, or N,N-dimethylformamide.Use of such a solvent however is not preferable as it is not onlyexpensive but also susceptible of penetrating through the skin andabsorbed in the human body, in other words, it is very, toxic.

Furthermore, when a laminate is produced with varnish containing such asolvent, the solvent will become a main cause for deteriorating theproperties of the laminate as it tends to remain in the final product tobe obtained upon heating and curing same.

Where a usual maleimide-type resin is employed for the production of acopper-lined laminate, the adhesion between a copper foil and thesubstrate is not always good and its workability such as blanking workis not satisfactory.

On the other hand, epoxy resins are extensively used as various electricinsulators, molded products, adhesive and paint since they can generallyafford, upon curing same with a wide variety of curing agents, curedproducts excellent in electrical characteristics, mechanicalcharacteristics, dimensional stability and chemical resistance.

However, depsite having such excellent properties, conventional epoxyresins are considered to be unsatisfactory with respect to resistance toheat. Thus, varied methods have been taken into consideration with aview toward enhancing their resistance to heat.

To obtain a resin excellent in varied properties and assuring bigcommercial utility by maintaining the advantageous features of these tworesins and simultaneously compensating for their drawbacks, it has beenattempted to incorporate a maleimide compound in epoxy resin. However,it was very difficult to obtain a uniform and stable composition whichis suitable for actual use, as conventional general maleimide compoundsare considerably poor in their miscibility with epoxy resins and, forexample, when formulated into varnish using a solvent, such varnishesare susceptible to separation and, when employed for solventlesscasting, the maleimide compounds tend to deposit as crystals.

SUMMARY OF THE INVENTION

An object of this invention is to provide a stable and uniformcomposition of at least one N-(alkenylphenyl)maleimide compound and oneor more kinds of epoxy resins.

Another object of this invention is to provide a curable resincomposition which can be formulated into a form suitable for applicationby using a commonly-used solvent of a relatively low boiling point.

A further object of this invention is to provide a curable resincomposition featuring improved work efficiency and facilitating theremoval of solvent from cured products.

A still further object of this invention is to provide a curable resincomposition capable of yielding a molded product having excellentresistance to heat and excellent mechanical strength at elevatedtemperatures.

N-(Alkenylphenyl)maleimides, their dimers and their polymers having apolymerization degree of at least 3 contain, besides unsaturated bondsof maleimido group, other unsaturated bonds originated from alkenylgroups or their polymers, which unsaturated bonds form strong bonds withthe epoxy compound or compounds or curing agent, whereby increasing thecrosslinking density of the resulting cured product and, corollary tothis, providing a molded product having excellent heat resistance andoutstanding mechanical strength at high temperatures. In a productobtained by curing a resin composition according to this invention, theheat resistance which is inherent to a general maleimide compound isfurther enhanced. In addition, the product maintains sufficiently theexcellent properties of an epoxy resin. Accordingly, it is equipped withproperties promising its application in the electronic field where ahigh degree of accuracy and reliability is required.

DETAILED DESCRIPTION OF THE INVENTION

The curable resin composition according to this invention comprises:

(a) at least one maleimide compound selected from the group consistingof N-(alkenylphenyl)malemides represented by the general formula (I):##STR1## wherein R¹ -R⁶ may be the same or different from one anotherand denote independently hydrogen, a hydrocarbon group having 1-20carbon atoms, a halogen, R⁷ O-- or ##STR2## group (where R⁷ represents ahydrocarbon group having 1-20 carbon atoms or a hydrocarbon group having1-20 carbon atoms and substituted by one or more halogen atoms of atleast one kind), hydroxyl group, cyano group, or a hydrocarbon groupsubstituted by one or more halogens, R⁷ O-- or ##STR3## group (where R⁷is as defined above), hydroxyl group or cyano group and having 1-20carbon atoms prior to the substitution, a plurality of R⁴ s may be thesame or different when m¹ stands for a value of 2 or greater, R⁵ may becoupled with either R¹ or R², thereby forming a ring, X denotes at leastone atom or group selected from hydrogen, halogens, hydroxyl group, R⁷O--, ##STR4## groups (where R⁷ is as defined above), cyano group, nitrogroup and carboxyl group, a plurality of Xs may be the same or differentwhen m² stands for a value of 2 or greater, and m¹, m² and m³ representindependently a positive integer and m¹ +m² +m³ =5, dimers of saidmaleimides and polymers of said maleimides having a polymerizationdegree of at least 3; and

(b) one or more kinds of epoxy resins, each having at least one epoxygroup in the unit molecule thereof.

Furthermore, the curable resin composition according to this inventionmay also contain, in addition to (a) at least one maleimide compoundrepresented by the above general formula (I) and (b) one or more kindsof epoxy resins, each, having at least one epoxy group in the unitmolecule thereof, (c) an amino compound represented by the generalformula (II):

    Q-(NH.sub.2).sub.n                                         (II)

wherein Q indicates an organic group having 1-150 carbon atoms and avalence of n, Q may contain at least one kind of atom selected fromhydrogen, oxygen, sulphur, halogen, nitrogen, phosphor and siliconatoms, and n stands for an integer of at least 1. This curable resincomposition may contain at least one kind of a prepolymer of at leastparts of any two components among components (a), (b) and (c).

The N-(alkenylphenyl)maleimide compounds, its dimers and its polymershaving a polymerization degree of at least 3 as well as their aminederivatives have excellent solubility to solvent compared with generalmaleimide compounds and their amine derivatives as well as extremelygood miscibility with epoxy resin. Owing to such solubility andmiscibility, as already mentioned above, the present inventors havesucceeded in obtaining a stable and uniform composition of a maleimidecompound and epoxy resin, which composition has scarcely been obtainedheretofore, through the use of a novel maleimido compound of the formula(I) as its maleimide component. Without depending on a polar organicsolvent such as N-methyl-2-pyrrolidone, N,N-dimethylformamide orN,N-dimethylacetamide which has been used for compositions containingconventional maleimide compounds, the resin composition according tothis invention may be satisfactorily applied by using a general organicsolvent of a relatively low boiling point. Thus, the resin compositionaccording to this invention not only leads to an improved workefficiency but also renders the removal of solvent from resultingproducts easy, and also provides a cured product of considerablyimproved quality.

As examples of N-(alkenylphenyl)maleimides represented by the abovegeneral formula (I) and usable in the present invention, there are:

N-(o-vinylphenyl)maleimide;

N-(m-vinylphenyl)maleimide;

N-(p-vinylphenyl)maleimide;

N-(o-isopropenyl)maleimide;

N-(m-isopropenylphenyl)maleimide;

N-(p-isopropenylphenyl)maleimide;

N-(vinyltolyl)maleimide, including all isomers thereof;

N-(isopropenyltolyl)maleimide, including all isomers thereof;

N-(p-α-ethylvinylphenyl)maleimide;

N-(m-α-ethylvinylphenyl)maleimide;

N-(p-α,β-dimethylbiphenyl)maleimide;

N-(m-α,β-dimethylvinylphenyl)maleimide;

N-(p-α-methyl-β-isopropylvinylphenyl)maleimide;

N-(m-α-methyl-β-isopropylvinylphenyl)maleimide;

N-(p-α-isobutylvinylphenyl)maleimide;

N-(m-α-isobutylvinylphenyl)maleimide;

N-(p-1-cyclohexenylphenyl)maleimide;

N-(m-1-cyclohexenylphenyl)maleimide;

N-(o-vinylphenyl)-3,4-dichloromaleimide;

N-(m-vinylphenyl)-3,4-dichloromaleimide;

N-(p-vinylphenyl)3,4-dichloromaleimide;

N-(p-isopropenylphenyl)-3,4-dichloromaleimide;

N-(m-isopropenylphenyl)-3,4-dichloromaleimide;

N-(o-isopropenylphenyl)-3,4-dichloromaleimide;

N-(p-isopropenylphenyl)-3,4-dibromomaleimide;

N-(p-isopropenylphenyl)-3,4-difluoromaleimide;

N-(4-vinyl-2-methoxyphenyl)maleimide;

N-(4-vinyl-3-methoxyphenyl)maleimide;

N-(4-isopropenyl-2-methoxyphenyl)maleimide;

N-(3-isopropenyl-4-methoxyphenyl)maleimide;

N-(4-vinyl-2-acetylphenyl)maleimide;

N-(4-isopropenyl-2-acetylphenyl)maleimide;

N-(4-vinyl-2-hydroxyphenyl)maleimide;

N-(4-isopropenyl-2-hydroxyphenyl)maleimide;

N-(4-isopropenyl-3-cyanophenyl)maleimide;

N-(4-isopropenyl-2-cyanophenyl)maleimide;

N-(4-vinyl-2-cyanophenyl)maleimide;

N-(p-α-chloromethyl-β-chlorovinylphenyl)maleimide;

N-(p-α-dichloromethyl-β-dichlorovinylphenyl)maleimide;

N-(p-α-bromomethyl-β-bromovinylphenyl)maleimide;

N-(p-vinylphenyl)-3-cyanomaleimide;

N-(p-vinylphenyl)-3,4-dicyanomaleimide;

N-(p-isopropenyl)-3,4-dicyanomaleimide;

N,N'-(1-vinyl-2,4-phenylene)bismaleimide;

N,N'-(1-vinyl-3,5-phenylene)bismaleimide;

N,N'-(1-isopropenyl-2,4-phenylene)bismaleimide;

N,N'-(1-isopropenyl-3,5-phenylene)bismaleimide;

N-(p-vinylphenyl)-3,4-di-t-butylmaleimide;

N-(p-isopropenylphenyl)-3,4-diisopropylmaleimide;

N-[4-α-(p-cyanophenyl)vinylphenyl]maleimide;

N-[4-α-methyl-β-(m-chlorophenyl)vinylphenyl]maleimide;

N-[4-α-(p-methoxyphenyl)vinylphenyl]maleimide;

N-[4-α-methyl-β-(m-acetylphenyl)vinylphenyl]maleimide;

N-[4-α-methyl-β-(p-hydroxyphenyl)vinylphenyl]maleimide;

N-(p-isopropenylphenyl)-3-(p-acetylphenyl)maleimide;

N-(p-vinylphenyl)-3-(p-methoxyphenyl)maleimide;

N-(m-isopropenylphenyl)-3-(p-chlorophenyl)maleimide;

2-isopropenyl-4-N-maleimido-4'-chlorobiphenyl;

4-isopropenyl-2-N-maleimido-4'-methylbiphenyl;

3-isopropenyl-4-N-maleimido-3'-methoxybiphenyl;

3-vinyl-4-N-maleimido-4'-hydroxybiphenyl;

3-isopropenyl-4-N-maleimido-4'-acetylbiphenyl;

2-N-maleimido-4-isopropenyl-4'-cyanobiphenyl;

N-(4-vinyl-3-nitrophenyl)maleimide;

N-(4-isopropenyl-3-carboxyphenyl)maleimide; and

N-(4-isopropenyl-3-acetylaminophenyl)maleimide.

In the present invention, dimers and/or trimers of the aboveN-(alkenylphenyl)maleimides may be used. As examples of such dimers ofN-(alkenylphenyl)maleimides, there may be mentioned linear dimers ofN-(p-isopropenylphenyl)maleimides, represented by the following formulae(III) and (IV): ##STR5## On the other hand, the polymers ofN-(alkenylphenyl)maleimides are not limited to any specific polymers,but such polymers desirously have a molecular weight not higher than10,000.

These dimers and polymers of N-(alkenylphenyl)maleimides are generallyprepared by dimerizing or polymerizing N-(alkenylphenyl)maleimides inthe presence of a suitable catalyst. Particularly in the case of alinear dimer and polymer of N-(p-isopropenylphenyl)maleimide, thefollowing production method may be followed. Namely, in a first step ofthe reaction process, a maleamic acid is prepared by causing maleicanhydride to react with the dimer or polymer of p-isopropenylanilinewhich has been obtained beforehand by heating p-isopropenylaniline in aninert organic solvent, if necessary, in the presence of an acidiccatalyst. Then, in a second step of the reaction process (i.e.,dehydrocyclization reaction), the dimer or polymer is imidated in thepresence of a catalyst into bismaleide or polymaleide. This two-stepprocess is known per se in the art.

As specific examples of an epoxy resin usable in the present inventionand having at least one epoxy group in its unit molecule, there may bementioned bisphenol-A epoxy resin, bisphenol-F epoxy resin, phenolnovolak epoxy resin, cresol novolak epoxy resin, alicyclic epoxy resins,heterocyclic epoxy resins such as triglycidylcyanurate,triglycidylisocyanurate and N,N-diglycidyl-5,5-dimethylhydantoin,hydrogenated bisphenol-A epoxy resins, aliphatic epoxy resins such aspropyleneglycol diglycidylether and pentaerythritol polyglycidylether,epoxy resins obtained from the reactions between aliphatic or aromaticcarboxylic acids and epihalohydrins such as epichlorohydrin, epoxyresins containing one or more spiro-rings, and glycidylether type epoxyresins which are reaction products of o-arylphenol novolak compounds andepichlorohydrin. In the various glycidyl compounds mentioned above, atleast some of the glycidyl groups may be β-methylglycidyl groups.

In the curable resin composition according to this invention, the weightratio of the epoxy resin to the maleimide compound is preferably in arange of 3:97-97:3, more preferably, 5:95-95:5. If the epoxy resin isused below its lower limit, excellent mechanical properties, goodadhesiveness to glass cloth or copper foil, good dimensional stabilityand preferred electrical characteristics, all inherent to epoxy resin,can be hardly recognized. Any product resulting from such a compositionis relatively brittle. Thus, the effects of this invention will be lost.On the other hand, if the epoxy resin is employed beyond its upperlimit, the effects of the maleimide component used in the presentinvention will not be recognized, particularly, resulting indeterioration of the heat resistance of a cured product to be obtained.

In the curable resin composition according to this invention, at leastparts of the maleimide compound and epoxy resin may be present in theform of a prepolymer thereof so long as the effects of this inventionare not hampered.

Although a curing agent for the epoxy resin is not necessarily essentialto the composition of this invention, it may be possible to employ sucha curing agent together with the epoxy resin as needed. Here, the curingagent may be employed in any suitable amount. However, it shall not beused in such an amount that it impedes the excellent effects derivedfrom the maleimido compound and epoxy resin respectively. The amount ofsuch a curing agent should thus be limited within such a range that itimproves the properties of the composition according to this invention.Among curing agents which may be employed as needed, there aretrifluoroboron-amine complexes such as trifluoroboron-monoethylaminecomplex and trifluoroboron-piperidine complex; tertiary amines such astriethylamine, benzylmethylamine, hexamethylene tetramine andN,N-dimethylaniline; quaternary ammonium salts such as tetramethylammonium bromide; borate compounds such as triphenyl borate andtricresyl borate; imidazole compounds such as N-methylimidazole,N-ethylimidazole, N-phenylimidazole and N-vinylimidazole; metalliccompounds such as zinc acetate, sodium acetate, cobalt naphtenate,titanium acetylacetonate, iron acetylacetonate, nickel acetylacetonate,sodium methylate, sodium ethylate and tetrabutoxy titanate; amide, ureaand melamine compounds obtained from amine compounds and carboxylic acidcompounds; dicyano diamides; phenol compounds such as phenol resinsobtained from reaction between bisphenol-A, bisphenol-F, bisphenol-S,pyrogallol, resorcine, catechol, hydroquinone or phenol and aldehydes orketones; isocyanate compounds such asmethylene-di-p-phenylene-diisocyanate, sulphoxy-m-phenylene-diisocyanateand tolylene-diisocyanate; cyanate compounds such asmethylene-di-p-phenylene-dicyanate, hydroxy-di-p-phenylene-dicyanate andsulphon-di-m-phenylene-dicyanate; anhydrides such as phthalic anhydride,hexahydrophthalic anhydride, tetrahydrophthalic anhydride,methyl-tetrahydrophthalic anhydride, methyl-hexahydrophthalic anhydride,nadic anhydride, methylnadic anhydride, chlorendic anhydride,dodecylsuccinic anhydride, methylsuccinic anhydride, benzophenonetetracarboxylic anhydride, pyromellitic anhydride and maleic anhydride.The curable resin composition according to this invention may alsocontain a radical polymerization initiator such as dicumyl peroxide,t-butyl perbenzoate, methylethyl ketone peroxide, orazo-bisisobutylonitrile as required.

Examples of amino compounds used in the present invention andrepresented by the above general formula (II) include the followingcompounds: aniline, toluidines, xylidines, vinylanilines,isopropenylanilines, phenylene diamines, diaminocyclohexane,2,4-diaminotoluene, 4,4'-diaminodiphenylmethane,3,4'-diaminodiphenylmethane, 2,2-bis(4'-aminophenyl)propane,4,4'-diaminodiphenylether, 4,4'-diaminodiphenylsulphide,4,4'-diaminodiphenylsulphone, 4,4'-diaminodicyclohexyl methane,m-xylylenediamine, p-xylylenediamine, bis(4-aminophenyl)diphenylsilane,bis(4-aminophenyl) methylphosphinoxide,bis(4-aminophenyl)methylphosphinoxide, tris(4-aminophenyl)thiophosphate,tris(4-aminophenyl)phosphate, 1,5-diaminonaphthalene, ethylene diamine,trimethylene diamine, tetramethylene diamine, hexamethylene diamine,nonamethylene diamine,4-methyl-2,4-bis(p-aminophenyl)pentene-1,4-methyl-2,4-bis(p-aminophenyl)pentene-2,as well as polymers of isopropenylanilines, polymers of vinylanilines,polyamines obtained through reactions between aromatic amines(forexample, aniline, toluidines, xylidines and anisidines) and aldehydes orketones(for instance, formaldehyde, acetaldehyde, and acetone),especially, poly(phenylmethylene) polyamine obtained from the reactionbetween aniline and formaldehyde.

As described above, the amino compound may be aliphatic, alicyclic oraromatic. It may be substituted by various substituents. In addition,the amino compound may contain in its molecule various metallicelements, or oxygen, halogens, sulphur, phosphorus or silicon.

There is no specific limitation to the amount of the amine to beemployed. However, the weight ratio of the amino compound to theN-(alkenylphenyl)maleimide compound component is preferably within arange of 3:97-97:3, more preferably, within a range of 5:95-95:5. If theamino compound is used below the lower limit thereof, the effectsexpected from the incorporation of the amino compound, for example, theeffects to further improve the excellent solubility of a compositionconsisting of the N-(alkenylphenyl)maleimide component and epoxy resinto solvent as well as to enhance the impact resistance of a resultingcured product would be scarcely recognized. On the other hand, if theamino compound is used beyond the upper limit thereof, the heatresistance of a resulting cured product would be substantially loweredand, when used as insulative varnish or in copper-lined laminates, thereis a danger that it would accelerate the corrosion of copper. It wouldalso be accompanied by another drawback that, when impregnated in glasscloth and formed into a laminate, the fluidity of the resin compositionwould become excessive. The optimum amount of the amino compound variesdepending on the number of double bonds of maleimido groups and groupsother than the maleimido groups in the maleimide component as well asthe number of epoxy groups in the epoxy resin.

The curable resin composition according to this invention comprises themaleimide compound of the general formula (I), epoxy resin and aminocompound of the general formula (II). It may be constituted by aprepolymer of any two components out of the three components and theremaining component so long as the effects of the invention are notimpeded.

Namely, after reacting the maleimide compound and amino compound inadvance, the reaction product may be mixed with the epoxy resin, therebyforming the curable resin composition of this invention. There is nospecific limitation to the mixing ratio of the maleimide compound andamino compound when they are reacted. However, the number ratio of allamino groups in the amino compound to all maleimido groups in themaleimide component(expressed by equation(V) below) is preferably notgreater than 1, more preferably, within a range of from 1 to 0.01.##EQU1## wherein, m_(i), n_(i) and M_(i) indicate, respectively, theamount of the maleimide compound used, the average number of maleimidogroups in its molecule, and its average molecular weight, whereas m_(a),n_(a) and M_(a) represent, respectively, the amount of the aminecomponent used, the average number of amino groups in its molecule andits average molecular weight.

The reaction between the maleimido compound and amino compound maygenerally be effected by either mixing both compounds directly withoutany solvent and heating same to an intimate mixture or reacting bothcompounds in the forms of homogeneous solutions or suspensions using asolvent. However, the reaction method shall not be limited to suchspecific reaction methods. The reaction is preferably carried out at atemperature of 50°-200° C. and for a period of 0-20 hours. Catalyst oradditives may also be added as needed.

It is also possible to prepare the curable resin composition accordingto this invention by first mixing and reacting the epoxy resin and aminocompound together and then combining the reaction product with themaleimide compound. In the reaction between the epoxy resin and aminocompound, the amino compound serves as a curing agent and is thuspolymerized to a higher molecular weight, thereby forming a productinsoluble to solvents and infusible. Thus, the ratio of amino groups toepoxy groups is suitably controlled and the reaction product is used asa prepolymer having a molecular weight in the range of 50-8,000,together with the maleimide compound and any other compounds which maybe incorporated as required. The curable resin composition according tothis invention may also be a composition containing as its constituentcomponent the product obtained by reacting a part of the epoxy resin anda part of the amino compound as described above as well as the remainingepoxy resin, amino compound and maleimide compound; or a compositioncontaining a prepolymer obtained by preliminarily reacting the maleimidecompound of the general formula (I) and the epoxy resin as well as theamino compound.

The curable resin composition according to this invention may be usedwith or without a solvent. When a solventless application method isadopted, it is merely mixed to a uniform mixture and then heated. Wherea solvent is used, the solvent may not necessarily be limited to anyspecific one, but examples of preferred solvents include: 3,4-dioxane,tetrahydrofuran, methylethyl ketone, acetone, methylisobutyl ketone,cyclohexane, chloroform, methylene chloride, trichloroethane, benzene,toluene, xylene, acetonitrile, 2-methoxyethanol, 2-ethoxyethanol,2-ethoxyethylacetate, diethyl ether, methylcellosolve, ethylcellosolve,etc. Of course, an intimately dissolved composition can be obtained byusing N,N-dimethylformamide, N,N-dimethylacetamide,N-methyl-2-pyrrolidone, dimethylsulphoxide, hexamethylphosphoroamide orthe like. However, such solvents are accompanied by serious drawbacks ashas already been mentioned above, it is preferable to avoid the use ofsuch solvents unless their use is indispensable due to special objectiveor limitation.

Where a solvent is employed, the concentration of all the resins mayvary depending on the application field of the composition and useconditions. In ordinary impregnating varnish, it ranges preferably from5-80%. For example, when used for the fabrication of laminates, anoverall resin concentration lower than 5% makes it difficult to cause arequired amount of the resin components to penetrate into glass cloth,thereby requiring to effect an impregnation step repeatedly on in alonger time period and considerably lowering the work efficiency. On theother hand, the presence of the resins in an amount beyond 80% of thecomposition is practically difficult to achieve in view of the limitedsolubility and miscibility of the resins. Even if such a composition isavailable, the viscosity of the solution would be considerably increasedand it would be difficult to be defoamed prior to its curing, therebyimpeding the work efficiency. A particularly preferred range of theoverall concentration of resins is from 10 to 70% by weight.

The composition according to this invention may also be employed in theform of emulsion or suspension.

To the composition according to this invention, the following componentsmay also be added, besides the maleimide compound, epoxy resin and theamino compound which may be used as required, and the reaction productof any two components of these three components:

(1) Powdery reinforcement agents, fillers and thickeners such asalumina, diatomaceous earth, magnesia, kaolin, magnesium carbonate,basic magnesium silicate, calcined clay, fine silica powder and carbonblack, as well as, fibrous reinforcement agents and fillers, forexample, inorganic fibers such as glass fibers, rock wool, ceramicfibers, asbestos and carbon fibers, pulp, wood flour, linter andpolyamide fibers. These powdery or fibrous reinforcement agents andfillers may be used in different amounts depending on the application ofthe composition and, where the composition is used for the fabricationof laminates or as a molding material, they may be added in an amount ofup to 4 times the total weight of the resins.

(2) A coupling agent such as, for example, vinyltriethoxysilane,vinyltris(β-methoxyethoxy)silane, γ-methacryloxypropyltrimethoxysilane,γ-glycidoxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane,N-(trimethoxysilylpropyl)ethylenediamine,N-(di-methoxymethyl-silylpropyl)ethylenediamine,γ-chloropropyltrimethoxysilane, vinyltrichlorosilane,β-3,4-epoxycyclohexylethyltrimethoxysilane, andγ-mercaptopropyltriethoxysilane. The coupling agent is generally addedin an amount ranging, preferably, 0.001-10.0%, and more preferably,0.01-5%, both on the basis of the total weight of the resins.

(3) A fire retardant and/or flame-resistant agent including, forexample, tetrabromobisphenol-A, tetrabromophthalic anhydride, brominatedepoxy resins(brominated bisphenol-A, brominated novolaks, and epoxidesof other halogenated compounds), decabromodiphenyl ether,hexabromobenzene, tetrabromoterephthalic acid, chlorinated paraffin,Diels-Alder adducts of hexachlorocyclopentadiene, red phosphorus,tricresylphosphate, esters of phosphonic acid, esters of phosphinicacid, phosphoroamidates, antimony trioxide, etc. They may be used withina range of, preferably 1-70%, and more preferably, 5-40%, both on thebasis of the total weight of the resins.

(4) One or more kinds of various natural and semi-synthetic substancesgenerally formulated in order to improve the properties of resins inadhesive layers, molded resin product, coating films including, forinstance, drying oil, semi-drying oil, oleoresin, rosin, shellac,oil-modified rosin, phenol resins, alkyd resins, urea resins, melamineresins, polyester resins, polyvinylbutyral resin, vinylacetate resin,vinyl chloride resin, acrylic resins and silicone resins. Such resinsmay be added as much as desired so long as they do not impede theproperties inherent to the resin composition of this invention. Namely,they may be added generally in an amount of not higher than 30% byweight of the total amount of the resins.

Curing conditions for converting the curable resin composition accordingto this invention into a cured product may vary depending on the typesof catalyst or resins actually used. They may also vary in accordancewith the form of the composition. The composition according to thisinvention is generally coated onto a substrate as adhesive or coatingfilm or formed or laminated in the form of powder or pellet, or in astate of being impregnated in a substrate, and then heated until cured.The curing temperature ranges generally 0°-300° C., and particularly,100°-250° C. The heating time for curing the composition is affected,especially, by the form of the composition and is generally within arange of from 30 seconds to 10 hours. It is necessary to apply heat fora time period sufficient to cure the resinous components completely.Where the composition according to this invention is used for thefabrication of a molded or otherwise shaped product, laminate or adheredstructure, it is desired to apply a pressure upon effecting theheat-curing. The pressure may range from 1 to 100 kg/m².

There is no particular limitation to be vested to the actual applicationform of the composition according to this invention. The following areexamples of formulations suitable for use as an impregnating varnish andfor use in laminates.

A homogeneous solution is prepared by mixing the maleimide compound andepoxy resin, and, optionally, the amino compound which may be added asrequired, and/or the prepolymer of any two kinds of components among thethree components with an organic solvent. It is preferred to use theseresins in such amounts that the total concentration of the resins fallswithin a range of 10-70%. To the thus-obtained solution, another curingagent, a silane-coupling agent and fire retardant may be added asrequired. Then, they are mixed uniformly into varnish.

The impregnating varnish resulting from the above-described operation isthen impregnated in a sheet-like reinforcement material such as glasscloth, glass sheet, non-woven glass fabric, asbestos sheet or the likeand, if required, dried in wind for a predetermined time period.Thereafter, it is dried in an oven maintained at 60°-160° C., therebyobtaining a prepreg (preimpregnate). The prepreg obtained with theuniform varnish prepared by the composition of this invention does notdevelop any separation of its components or foams and, moreover, haspreferable dryness to touch. The thus-obtained prepreg can be storedstably over a long period of time at room temperature. A plural sheetsof such prepreg are then superposed and, if necessary, a copper foil orcopper foils may be applied onto either upper or lower surface of thethus-superposed prepreg or onto both upper and lower surfaces thereof.Thereafter, it is formed under pressure for a certain period of time ina compression-molding machine at a temperature of 100°-250° C. and apressure of 1-100 kg/cm².

During this compression molding, the resins are fused and exhibit asuitable degree of low characteristics, thereby facilitating the uniformimpregnation of the resins. The resins are thus cured as mentioned aboveand a laminate or copper-lined laminate of good quality is provided.

The present invention will now be described further in the followingexamples:

EXAMPLE 1

4-Methyl-2,4-bis(p-N-maleimidophenyl)pentene-1 and DEN-431(trade mark,novolak epoxy resin produced by Dow Chemical Company), respectively inthe amounts of 38.5 g and 16.5 g, were uniformly dissolved in 45 g oftetrahydrofuran. The thus-prepared varnish was impregnated in glasscloth (thickness: 0.18 mm) and dried for 20 minutes at 100° C., therebyobtaining a preimpregnate. Nine sheets of the thus-preparedpreimpregnates were superposed and a sheet of copper foil was thenplaced on the top of the preimpregnates. At a press pressure of 40kg/cm², it was heated by raising its temperature from 100° C. to 180° C.over 30 minutes and further heated at 180° C. for one hour, providing acopper-lined laminate. This laminate was subjected to after-curing for10 hours in an oven of 220° C.

Table 1 shows the resistance of the resulting laminate to the heat ofsoft solder and the anti-peeling strength of the copper foil.

EXAMPLE 2

In 61.4 g of methylethyl ketone, were dissolved 42.6 g ofN-(p-isopropenylphenyl)maleimide oligomer(composition: monomer 2.7%,dimer 77.3%, trimer 6.7%, tetramer and higher polymers 13.3%), 9.9 g of4.4'-diaminodiphenylmethane and 22.5 g of Epikote-828(trade mark;bisphenol-type epoxy resin produced by Shell International ChemicalInc.). Glass cloth(thickness: 0.18 mm) was impregnated with thethus-prepared varnish and then dried at 95° C. for 15 minutes, therebyproviding a preimpregnate. Nine sheets of the thus-preparedpreimpregnates were superposed and a sheet of copper foil was thenplaced on the top of the preimpregnates. It was thereafter pressed,bonded under pressure, and cured in accordance with the followingconditions. Namely, at a press pressure of 40 kg/cm², it was heated byraising its temperature from 100° C. to 180° C. over 30 minutes andmaintained at 180° C. for further one hour.

Table 1 also shows the resistance of the resulting laminate to the heatof soft solder and the anti-peeling strength of the copper foil.

EXAMPLE 3

After thoroughly grinding and mixing 213 g of the linear dimer mixtureof N-(p-isopropenylphenyl)maleimides consisting of 89.5% of4-methyl-2,4-bis(p-N-maleimidophenyl) pentene-1 and 10.5% of4-methyl-2,3-bis(p-N-maleimidophenyl) pentene-2 and 50 g of4,4'-diaminodiphenylmethane, the resulting mixture was heated at 125° C.to a fused state, in which they were reacted to each other for 20minutes. Subsequent to cooling down the reaction product and grindingthe same, the resulting 44 g of powder and 11 g of DEN-431 weredissolved in 45 g of 1,4-dioxane, thereby providing varnish.

The thus-prepared varnish was used to produce a laminate under the sameconditions as in Example 1. The resistance of the laminate to the heatof soft solder and the anti-peeling strength of the copper foil weremeasured. Measurement results are also shown in Table 1.

COMPARATIVE EXAMPLE 1

Powder obtained by thoroughly grinding and mixing 89.6 g ofN,N'-(methylene-di-p-phenylene)bismaleimide and 24.8 g of4,4'-diaminodiphenylmethane was heated to 120° C., thereby fusing sameand then reacting the compounds to each other for 10 minutes. Thereaction product was then cooled down to solid. The resulting solid wasground again, providing 41 g of powder, which was then dissolvedtogether with 10 g of DEN-431 in 45 g of N,N-dimethylformamide,resulting in varnish. Glass cloth(thickness: 0.18 mm) was impregnatedwith the varnish and dried at 160° C. for 20 minutes, thereby obtaininga preimpregnate. Nine sheets of the thus-obtained preimpregnates weresuperposed and a sheet of copper foil was then placed on the top of thepreimpregnates. At a press pressure of 40 kg/cm², it was heated byraising its temperature from 120° C. to 180° C. over 30 minutes and thenheated at 180° C. for further one hour, resulting in a copper-linedlaminate.

The resistance of the laminate to the heat of soft solder and theanti-peeling strength of the copper foil are also shown in Table 1.

COMPARATIVE EXAMPLE 2

In 45 g of N-methyl-2-pyrrolidone, were intimately dissolved 41 g ofN,N'-(methylene-di-p-phenylene)bismaleimide and 14 g of EPN-1138(trademark; novolak-type epoxy resin produced by Ciba-Geigy AG). Acopper-lined laminate was prepared under conditions similar to thoseused in Comparative Example 1. Its resistance to the heat of soft solderand the anti-peeling strength of the copper foil are shown in Table 1.

                  TABLE 1                                                         ______________________________________                                                    Example No.                                                       Property      1       2      3     1*    2*                                   ______________________________________                                        Resistance to heat of                                                                       130     120    127   100   115                                  soft solder (300° C.)                                                  (sec)                                                                         Anti-peeling strength                                                                       1.32    1.57   1.51  1.21  1.09                                 of copper foil                                                                (kg/cm)                                                                       ______________________________________                                         *Comparative Example                                                     

EXAMPLE 4

In 50 g of methylethyl ketone, were dissolved 47 g ofN-(p-isopropenylphenyl)maleimide oligomer(composition: monomar 3.7%,dimer 83.3%, trimer 5.1%, tetramer and higher polymers 7.9%) and 3 g ofEpikote(trade mark; bisphenol-type epoxy resin produced by ShellInternational Chemicals Inc.) to form varnish. The stability of thevarnish was determined by virtue of variations in its viscosity. Resultsare shown in Table 2.

COMPARATIVE EXAMPLE 3

With 50 g of methylethyl ketone, were mixed 47 g of a prepolymerproduced from N,N'-(methylene-di-p-phenylene) bismaleimide and4,4'-diaminodiphenylmethane as in Comparative Example 1. However, thelatter were insolble to the former. Substitution of 50 g ofN-methyl-2-pyrrolidone for methylethyl ketone resulted in a uniformsolution. The stability of the thus-prepared varnish was determinedthrough measuring its viscosity. Results are also shown in Table 2.

                  TABLE 2                                                         ______________________________________                                                  Number of days allowed to stand                                               0     7         14      21                                          ______________________________________                                        Example 4   ≦0.5                                                                            0.5       0.5   0.5                                      Comparative 8.8     17.6      36.2  63.4                                      Example                                                                       ______________________________________                                         Note 1: unit poise (25° C.)                                            Note 2: Measurement method bubble viscometer (GardnerHoldt method)       

EXAMPLE 5

In 100 g of methylethyl ketone, were dissolved 80 g ofN-(p-isopropenylphenyl)maleimide oligomer(composition: monomer 3.7%,dimer 83.3%, trimer 5.1%, tetramer and higher polymers 7.9%), 20 g ofEpikote-828, 5.5 g trimellitic anhydride and 1.1 g of4,4'-diaminodiphenylsulphone to form a uniform solution. Then,methylethyl ketone was allowed to evaporate from the solution at 50° C.and at a reduced pressure, leaving a resin composition. This compositionwas poured into a mold which had been in advance coated with a partingagent and maintained at 110° C. The mold was made of stainless steel. Itwas then degasified under a reduced pressure and, thereafter, pressedunder a pressure of 70 kg/cm² and slowly heated and cured, first at 170°C. for one hour and then at 200° C. for 3 hours. After cooling down thethus cured molded product to room temperature, it was withdrawn from themold and a resin plate (i.e., test specimen) of 3 mm× 100 mm×100 mm wasobtained. The thermal deformation temperature, dielectric constant anddielectric loss tangent of the thus-cured resin plate were respectively312° C., 2.84 (1 MHz, at 25° C.) and 0.011 (1 MHz, at 25° C.). Anotherresin plate (4 mm×10 mm×100 mm) prepared similarly had bending strengthof 16.3 kg/mm² at 25° C.

What is claimed is:
 1. A curable resin composition comprising:(a) atleast one maleimide compound selected from the group consisting ofN-(alkenylphenyl)maleimides represented by the general formula (I):##STR6## wherein R¹ -R⁶ are the same or different from one another anddenote independently hydrogen, a hydrocarbon group having 1-20 carbonatoms, a halogen, R⁷ O-- or ##STR7## group where R⁷ represents ahydrocarbon group having 1-20 carbon atoms or a hydrocarbon group having1-20 carbon atoms and substituted by one or more halogen atoms, hydroxylgroup, cyano group, or a hydrocarbon group substituted by one or morehalogens, R⁷ O-- or ##STR8## group, hydroxyl group or cyano group andhaving 1-20 carbon atoms prior to the substitution, a plurality of R⁴ sare the same or different when m¹ stands for a value of 2 or greater, R³is coupled with either R¹ or R², thereby forming a ring, X denotes atleast one atom or group selected from hydrogen, halogens, hydroxylgroups, R⁷ O-- ##STR9## groups, where R⁷ is as defined above, cyanogroup, nitro group or carboxyl group, a plurality of Xs are the same ordifferent when m² stands for a value of 2 or greater, and m¹, m², and m³represent independently a positive integer and m¹,+m² +m³ =5, dimers ofsaid maleimides and polymers of said maleimides having a polymerizationdegree of at least 3; (b) at least one epoxy compound, each having atleast one 1,2 epoxy group in the unit molecule thereof; and, (c) anamino compound represented by the general formula (II):

    Q-(NH.sub.2).sub.n                                         (II)

wherein Q indicates an organic group having 1-150 carbon atoms and avalence of n, Q contains at least one kind of atom selected fromhydrogen, oxygen, sulphur, halogen, nitrogen, phosphorus or siliconatoms, and n represents an integer of at least 1, and said compositioncontains at least one kind of a prepolymer of at least parts of any twocomponents among components (a), (b) and (c).
 2. A curable resincomposition as claimed in claim 1, wherein said amino compound is anamino compound containing one or more benzene rings.
 3. A curable resincomposition as claimed in claim 1, wherein said amino compound is areaction product of aniline and formaldehyde.
 4. A curable resincomposition as claimed in claim 1, wherein said amino compound is4,4'-diaminodiphenyl methane.
 5. A curable resin composition as claimedin claim 1, wherein the weight ratio of component (c) to component (a)ranges from 3:97 to 97:3.
 6. A curable resin composition as claimed inclaim 1, wherein the prepolymer is formed by a part of component (c) anda part of component (a) and the weight ratio of component (c) tocomponent (a) in said prepolymer is such that the number ratio of allamino groups in component (c) in the prepolymer to all maleimido groupsin component (a) in the prepolymer is 1 or less.
 7. A curable resincomposition as claimed in claim 6, wherein said composition furthercomprises one or more resins selected from the group consisting ofdrying oil, semidrying oil, oleoresin, rosin, shellac, oil-modifiedrosin, phenol resins, alkyd resins, urea-formaldehyde resins,melamine-formaldehyde resins, unsaturated polyester resins,polyvinylbutyral resins, vinylacetate resins, vinylchloride resin,acrylic resins and silicone resins, and said one or more resins arecontained in total in an amount of not more than 30% of the weight ofthe entire resins.
 8. A curable resin composition as claimed in claim 1,wherein said maleimide compound is at least one maleimide compoundselected from the group consisting of N-(p-isopropenylphenyl)maleimide,dimers thereof and polymers thereof having a polymerization degree of atleast
 3. 9. A curable resin composition as claimed in claim 1, whereinsaid maleimide compound is at least one dimer orN-(p-isopropenylphenyl)maleimide.
 10. A curable resin composition asclaimed in claim 9, wherein the linear dimer ofN-(p-isopropenylphenyl)maleimide is at least one dimer selected from4-methyl-2,4-bis(p-N-maleimidophenyl)pentene-1 or4-methyl-2,4-bis(p-N-maleimidophenyl)pentene-2.
 11. A curable resincomposition as claimed in claim 1, wherein component (a) is a mixture ofN-(isopropenylphenyl)maleimide, dimers thereof and one or more ofpolymers thereof having a polymerization degree of at least
 4. 12. Acurable resin composition as claimed in claim 11, wherein said mixturecontains at least 70% of dimers of N-(p-isopropenylphenyl)maleimide. 13.A curable resin composition as claimed in claim 1, wherein said epoxyresins include at least one epoxy resin containing benzene rings.
 14. Acurable resin composition as claimed in claim 1, wherein said epoxyresins include at least one bisphenol-type epoxy resin.
 15. A curableresin composition as claimed in claim 1, wherein said epoxy resinsinclude at least one novolak-type epoxy resin.
 16. A curable resincomposition as claimed in claim 1, wherein the weight ratio of component(b) to component (a) ranges from 3:97 to 97:3.
 17. A curable resincomposition as claimed in claim 1, wherein said composition issubstantially free of solvent.
 18. A curable resin composition asclaimed in claim 1, wherein said composition further comprises anorganic solvent.
 19. A curable resin composition as claimed in claim 1,wherein said composition further comprises at least one solvent compoundselected from the group consisting of tetrahydrofuran, methylethylketone, 1,4-dioxane, acetone, methylisobutyl ketone, dichloromethane,trichloroethane, benzene, toluene, xylene, acetonitrile,2-methoxyethanol, 2-n-butoxyethanol, 2-ethoxyethylacetate, diethylether,methylcellosolve, ethylcellosolve, N,N-dimethylformamide,N,N-dimethylacetamide and N-methyl-2-pyrrolidone.
 20. A curable resincomposition as claimed in claim 1, wherein said composition furthercomprises at least one solvent compound selected from the groupconsisting of tetrahydrofuran, methylethyl ketone, 1,4-dioxane, acetone,acetonitrile, methylcellosolve, and ethylcellosolve.
 21. A curable resincomposition as claimed in claim 1, wherein said composition furthercomprises one or more powdery materials other than resins and saidpowdery materials are contained in total in an amount up to 4 time theweight of the entire resins.
 22. A curable resin composition as claimedin claim 1, wherein said composition further comprises a coupling agentin an amount of 0.001-10% by weight of the entire resins.
 23. A curableresin composition as claimed in claim 1, wherein said compositionfurther comprises a coupling agent in an amount of 0.01-5% by weight ofthe entire resins.
 24. A curable resin composition as claimed in claim1, wherein said composition further comprises at least one kind of fireretardants and flame resistant agents in an amount of 1-70% by weight ofthe entire resins.
 25. A curable resin composition as claimed in claim1, wherein said composition further comprises at least one kind of fireretardants and flame resistant agents in an amount of 5-40% by weight ofthe entire resins.
 26. A curable resin composition as claimed in claim1, wherein said composition further comprises a curing agent forcomponent (b).
 27. A curable resin composition as claimed in claim 1wherein said composition further comprises a radical polymerizationinitiator.
 28. A curable resin composition as claimed in claim 1,wherein said maleimide compound is at least one linear dimer ofN-(p-isopropenylphenyl)maleimide, the linear dimer being selected fromthe group consisting of: ##STR10##